21mm oko midrange stutter

[welder steve]

Ok the thing idles like a beast and will take off wheel high but beyond the initial jump it * and stutters and if i go above 1/2 throttle it bogs and falls on its face. Af16, 48 rumia kit,ct manifold, black oko 21mm,pod filter,122,45 jetting, stock exhaust derestricted , zx trans , 1500 clutch and contra springs, 3.5 tire on a ruckus rim, any ideas ? Oh and im running premix. Thanks in advance

[maddog]

I just had the same problem, it was a bad coil after 5,000 rpm- so when people think that 2 stroke engines are simple they are infact complicated.

[welder steve]

Ah im going to try that in the morning have a coil that throws fire sitting on the bench

[Wheelman-111]

Greetings:

That jetting worked for me in a 26, might be a mite rich in a 21. What color is the spark plug? What temps? What number spark plug?

[welder steve]

Running a ngk 6, plug is kinda dark on the ground strap from a stop it will throw you off then start stuttering then wot bog

[Downsouthdio]

That seems a little to much on the main, and pilot..do you have different jets to try?

[welder steve]

I have a 110 main also and complete set of pilot jets was jetting rich as i am riding it any time it gets over 40

[welder steve]

Mabey im fat on the jet and needle

[Wheelman-111]

Greetings:

Wheelman's Rules of Jetting:

1. The correct jet for your build is always the one you don't have.
2. Avoid making more than one change at a time

At 75ccs, the 110 is almost certainly too small particularly if it's a high-revving build. You could consider dropping the jet needle all the way down (leanest) and see if it's even a little bit better. If so, consider a 118-120 replacing the needle where it was. If not, consider a 42 Pilot, once again leaving everything else the way it is. Unless it' cold in your area, may I suggest a #8 spark plug too.

[swimmingfree]

this may help as well as a plug crop the best color is a candy bar color ..
swimmingfree

[Wheelman-111]

Greetings:

We've seen that chart many times, and while it's a good general guide, I disagree with the following:

It shows the "Air Screw/Slow JET" signing off just before half throttle. Like it just Quits! I've found it ain't necessarily so. A big Pilot, which we tend to use in these over-carbed little engines, keeps slinging its mist down the throat all the way to full throttle. True, the quantity of fuel sprayed is not as abundant as the issue from the Main, but for sure the Pilot doesn't stop spraying just because the throttle is open wide either. So much so that a smaller Pilot somtimes requires a raised needle position or even a bigger Main, and vice-versa.

[welder steve]

Yeah im in michigan so its pretty cold right now , wont be getting out until the snow quits i want to get this thing on the road turning some rpms

[Meejacob]

Try get some needle jets, I was running a 21 Oko on my 72 malossi cast and I had to change my needle to go any where after like 1/2 throttle

[welder steve]

Hmm i was thinking of trying a different needle wonder if other keihin carbs use the same needle as ive got a few kehin round slide 20 and 22mm lying around with new needles in them. Thanks for all of the replys guys. Also i think my stock exhaust is being a huge bottle neck, its derestricted but im in need of a good pipe.

[welder steve]

Well dropped to a 100 main and needle 2 from top with 45 pilot. Still a lil stutter changer to 6 plug, and installed a pg long and this ithing is a beast runs great but likes to die if i sit at a light too long? Changed frim 5 gram sliders to 7.1 rollers ha little heavy but still rockets with stock gears .wonder why it wants to bog out after